全文获取类型
收费全文 | 1029篇 |
免费 | 2篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 77篇 |
机械仪表 | 7篇 |
建筑科学 | 7篇 |
能源动力 | 4篇 |
轻工业 | 8篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 34篇 |
一般工业技术 | 65篇 |
冶金工业 | 776篇 |
原子能技术 | 3篇 |
自动化技术 | 43篇 |
出版年
2023年 | 2篇 |
2021年 | 5篇 |
2019年 | 3篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 33篇 |
1998年 | 235篇 |
1997年 | 135篇 |
1996年 | 89篇 |
1995年 | 57篇 |
1994年 | 37篇 |
1993年 | 44篇 |
1992年 | 14篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 17篇 |
1976年 | 42篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1967年 | 1篇 |
排序方式: 共有1031条查询结果,搜索用时 140 毫秒
991.
SH Snook BS Webster RW McGorry MT Fogleman KB McCann 《Canadian Metallurgical Quarterly》1998,23(23):2601-2607
STUDY DESIGN: Eighteen-month, randomized controlled trial with partial crossover. OBJECTIVES: To test the hypothesis that the control of lumbar flexion in the early morning will significantly reduce chronic, nonspecific low back pain. SUMMARY OF BACKGROUND DATA: Previous studies have indicated an increased risk of low back pain with bending forward in the early morning, primarily because of increased fluid content in the intervertebral discs at that time. METHODS: After 6 months of recording baseline data, 85 subjects with persistent or recurring low back pain were randomly assigned to treatment and control groups. The treatment group received instruction in the control of early morning lumbar flexion. The control group received a sham treatment of six exercises shown to be ineffective in reducing low back pain. Six months later, the control group received the experimental treatment, Diaries were used to record daily levels of pain intensity, disability, impairment, and medication usage. RESULTS: Significant reductions in pain intensity (P < 0.01) were recorded for the treatment group, but not for the control group (point estimate, 33%; 95% confidence interval, 11-55%). After receiving the experimental treatment, the control group responded with similar reductions (P < 0.05). Significant reductions also were observed in total days in pain, disability, impairment, and medication usage. CONCLUSIONS: Controlling lumbar flexion in the early morning is a form of self-care with potential for reducing pain and costs associated with chronic, nonspecific low back pain. 相似文献
992.
RB Burns EP McCarthy KM Freund SL Marwill M Shwartz A Ash MA Moskowitz 《Canadian Metallurgical Quarterly》1996,44(8):922-926
OBJECTIVE: To determine rates of and explore factors associated with mammography use among older women. DESIGN: Retrospective review of part B (physician) bills submitted to Medicare during 1990. SETTING: Health Care Financing Administration (HCFA) data, including sociodemographic information and part B physician bills for all services delivered to Medicare-eligible women in 1990. PATIENTS/PARTICIPANTS: Women age 65 or older as of January 1, 1990, residing in one of 10 states with part B coverage through December 31, 1990. MEASUREMENTS AND MAIN RESULTS: The outcome was receipt of a mammogram (yes/no). We explored factors associated with mammography use within three age groups: 65 to 74, 75 to 84, and 85+. The factors considered were race, state, median income of ZIP Code of residence (from the 1990 US Census, and used to divide the population into quintiles within each state), and number of primary care visits (0, 1, 2, and 3+). Overall, 15% of women had a mammogram: 20% of women age 65 to 74, 12% of women age 75 to 84, and 4% of women age 85 and older. Mammography use was lowest in Oklahoma and highest in Washington. However, in each state the older the age category, the less the mammography use (e.g., 9% vs 5% vs 2% in Oklahoma and 25% vs 16% vs 5% in Washington for women 65-74, 75-84, and 85+, respectively). Mammography use was lower for black than for white women age 65 to 74 (14% vs 21%, P < .001) and 75 to 84 (9% vs 12%, P < .001). Women in each of these two age groups had lower mammography use if they resided in the lowest income quintile and highest if they resided in the highest income quintile (17% vs 23% 65-74, and 10% vs 13% 75-84, P values < .001). Among the oldest women (those 85+), mammography use was low (4%) and varied minimally by race and income (P = .907 and .003, respectively). In all age groups, mammography use was lowest among women who did not have a primary care visit, was greater among women who had at least one visit, and continued to rise with increasing numbers of visits (all P values < .001). For example, among women age 75 to 84, mammography use increased from 5% to 10%, 14%, and 17% for those with 0, 1, 2, and 3+ visits. CONCLUSIONS: We found that mammography use was less for women who were older, of black race, who did not visit a primary care provider, and who lived in areas with lower median income and certain geographic locations (states). Similar factors influenced mammography use in women age 65 to 74, where there is greater consensus as to who should receive a mammogram, and women age 75 to 84, where there is neither consensus nor data. Surprisingly, neither race nor income had much influence on mammography use among women age 85 or older. 相似文献
993.
KB Wells 《Canadian Metallurgical Quarterly》1994,35(3):279-296
Prepaid or prospective reimbursement has implications for the consultation-liaison (C-L) psychiatrist. The author reviews results from three health policy studies that indicated 1) degree of reliance on general medical providers for mental health care is not affected by generosity of fee-for-service (FFS) coverage, but is greater in some prepaid health care systems; 2) psychological sickness of depressed outpatients visiting general medical providers is similar across prepaid and FFS systems of care; 3) prepaid care is associated with lower rates of detection of depression and counseling in the general medical sector; 4) depression outcomes in the general medical sector are similar under prepaid or FFS care; 5) quality of care for depressed patients is moderate to low in the general medical sector; and 6) depressed elderly inpatients receive higher quality of psychological care in psychiatric units, but they receive higher quality of physical care in general medical wards. The discussion emphasizes the C-L psychiatrist's role in educating general medical providers, improving outcomes for the sickest patients, and improving psychosocial care in prepaid practices. 相似文献
994.
995.
JC McCann R Kanteti B Shilepsky KB Miller M Sweet DP Schenkein 《Canadian Metallurgical Quarterly》1996,2(1):37-43
Treatment of cultured bovine adrenal chromaffin cells with dbcAMP increased [3H]STX binding with an EC50 of 126 microM and a half-effective time of 12 h; dbcAMP (1 mM x 18 h) raised the Bmax approximately 1.5-fold without altering the Kd value. Forskolin (0.1 mM) or IBMX (0.3 mM) also increased [3H]STX binding, while dbcGMP had no effect. Effects of dbcAMP and forskolin were abolished by H-89, an inhibitor of cAMP-dependent protein kinase. Cycloheximide (10 microgram/ml) and actinomycin D (10 microgram/ml), inhibitors of protein synthesis, nullified the stimulatory effect of dbcAMP, whereas tunicamycin, an inhibitor of protein glycosylation, had no effect. Treatment with dbcAMP augmented veratridine-induced 22Na influx, 45Ca influx via voltage-dependent Ca channels and catecholamine secretion, while the same treatment did not alter 45Ca influx and catecholamine secretion caused by high K (a direct activation of voltage-dependent Ca channels) [25]. Na influx via single Na channel calculated from 22Na influx and [3H]STX binding was quantitatively similar between non-treated and dbcAMP-treated cells. Brevetoxin allosterically enhanced veratridine-induced 22Na influx approximately 3-fold in dbcAMP-treated cells as in non-treated cells. These results suggest that cAMP-dependent protein kinase is involved in the modulation of Na channel expression in adrenal medulla. 相似文献
996.
P Hasler N Brot H Weissbach W Danho Y Blount JL Zhou KB Elkon 《Canadian Metallurgical Quarterly》1994,72(2):273-279
The immunodominant epitope recognized by lupus antiribosomal P protein antibodies (anti-P antibodies) is located within the 11 C-terminal residues common to the three P proteins. This epitope contains a potential phosphorylation site for casein kinase II and clusters of acidic and hydrophobic amino acids. To determine the role of each of these features in antigen recognition, lupus anti-P sera were tested for binding to phospho- and dephospho- forms of the P proteins and to synthetic peptide antigens in which site-specific modifications had been introduced. Immunoblot analysis revealed that anti-P antibodies specific for the phospho- form of the P proteins represented only a minor population of anti-P antibodies and, in many cases, were absent altogether. In contrast, when charged substitutions were introduced into either the acidic or hydrophobic clusters and tested by ELISA, striking reductions of 64-86% were observed. Conservative Gly-->Pro substitutions also produced a 73% average reduction in anti-P binding whereas substitution of either Ser-105 or the C-terminal Asp-115 resulted in a < 35% reduction in binding. These findings suggest that phosphorylation of the P proteins does not play a role in antibody recognition but that anti-P antibodies require both the acidic and hydrophobic clusters for optimal binding to synthetic peptide antigens. The remarkable degree of specificity demonstrated by these antibodies supports the view that anti-P autoantibodies result from a highly specific (at the B cell level) immune response to self antigen. 相似文献
997.
998.
TM Nakamura GB Morin KB Chapman SL Weinrich WH Andrews J Lingner CB Harley TR Cech 《Canadian Metallurgical Quarterly》1997,277(5328):955-959
999.
1000.
KB Kern RW Hilwig RA Berg KH Rhee AB Sanders CW Otto GA Ewy 《Canadian Metallurgical Quarterly》1997,95(12):2610-2613
BACKGROUND: Global left ventricular dysfunction after successful resuscitation is well documented and appears to be a major contributing factor in limiting long-term survival after initial recovery from out-of-hospital sudden cardiac death. Treatment of such postresuscitation myocardial dysfunction has not been examined previously. METHODS AND RESULTS: Systolic and diastolic parameters of left ventricular function were measured in 27 swine before and after successful resuscitation from prolonged ventricular fibrillation cardiac arrest. Dobutamine infusions (10 micrograms.kg-1.min-1 in 14 animals or 5 micrograms.kg-1.min-1 in 5 animals) begun 15 minutes after resuscitation were compared with controls receiving no treatment (8 animals). The marked deterioration in systolic and diastolic left ventricular function seen in the control group after resuscitation was ameliorated in the dobutamine-treated animals. Left ventricular ejection fraction fell from a prearrest 58 +/- 3% to 25 +/- 3% at 5 hours after resuscitation in the control group but remained unchanged in the dobutamine (10 micrograms.kg-1.min-1) group (52 +/- 1% prearrest and 55 +/- 3% at 5 hours after resuscitation). Measurement of the constant of isovolumic relaxation of the left ventricle (tau) demonstrated a similar benefit of the dobutamine infusion for overcoming postresuscitation diastolic dysfunction. The tau rose in the controls from 28 +/- 1 milliseconds (ms) prearrest to 41 +/- 3 ms at 5 hours after resuscitation whereas it remained constant in the dobutamine-treated animals (31 +/- 1 ms prearrest and 31 +/- 5 ms at 5 hours after resuscitation). CONCLUSIONS: Dobutamine begun within 15 minutes of successful resuscitation can successfully overcome the global systolic and diastolic left ventricular dysfunction resulting from prolonged cardiac arrest and cardiopulmonary resuscitation. 相似文献